

$arr:10px 20px 30px;
.box1{ 
    margin-top: nth($arr,1);
    margin-left: nth($arr,2);
}

$arr2:left top right bottom;
.box2{ 
    .#{nth($arr2,2)}{ 
        color: red;
        margin-#{nth($arr2,1)}:10px;
    }
}

$obj:('t':'top','l':'left','w':500px);
.box3{ 
    width: map-get($obj,'w');
    margin-#{map-get($obj,'t')}:20px;
}